This invention relates to aircraft fuel systems and, more particularly, to increasing a cooling capacity of fuel within the fuel system to cool heat-producing aircraft components.
Fuel is widely known and used in the aircraft industry as a heat sink before combustion for cooling heat-producing aircraft components. For example, in aircraft having gas turbine engines, the fuel is used to cool bleed air from an engine compressor in a cabin air cycle control system, heat-producing aircraft components in a thermal management system, or an engine turbine in a turbine film cooling system.
To extend the usefulness of the fuel as a coolant, there have been proposals to treat the fuel to increase the cooling capacity. For example, the cooling capacity of dissolved oxygen-rich fuel is limited because the oxygen initiates formation of deposits commonly referred to as “coke” or “coking” at temperatures between 350° F. and 850° F. Typically, lowering the oxygen concentration overcomes the coking problem and allows the fuel to be heated without significant coking. Thus, an oxygen-depleted or “deoxygenated” fuel can be heated to a higher temperature without coking to provide increased cooling capacity.
For some aircraft, an even greater cooling capacity is desired. For example, hypersonic aircraft or other types of propulsion devices, components or engines (e.g., scramjet engines) may operate at temperatures near or above 850° F. and up to about 1700° F. At such temperatures, the traditional fuel treatment may not provide fuel having enough cooling capacity to cool the aircraft components or engine to a desired temperature without coking. Therefore, there is a need for a fuel system and method for increasing the cooling capacity of the fuel.